Control track recording and synchronizing system



Sept. 28, 1943,

CONTROL TRAGK RECORDING AND SYNCHRONIZ ING SYSTEM Filed Jan. 29, 1941 A.c. BLANEY v 2,330,331 A INVENTOR: 1 A2 Hue FLA/V5);

BY W f (ATTORNEYS.

Patented Sept. 28, 1943 CONTROL TRACK RECORDING AND ,SYNCHRONIZINGSYSTEM Arthur C. Blaney, Los Angeles, Calif., assignor to RadioCorporation of America, a corporation of Delaware Application January29, 1941, Serial No. 376,521

9 Claims.

This invention relates to sound recording and reproducing systems andparticularly to a system for producing a control record for a signalrecord and for marking or synchronizing the two records for subsequentcombination.

It is well known in the art that the level of a film sound record, maybe controlled during reproduction by another photographic recordseparate from the signal record or by a record contained on the samefilm strip. Such a type of signal and control film record combination isdisclosed in copending application Serial No.

181,634, filed December 24, 1937, wherein the control record isinterposed between the sprocket hole perforations, these perforationsbeing used to produce a 96-cycle carrier frequency for controlling theamplification of the signal record.

The present invention is directed to a system for producing a controlrecord of a certain signal record after the signal record has been made.That is, after a signalrecord of sound efiects or background noises hasbeen recorded (it is also applicable to a sound record of'dialogue or acombination record of dialogue and background effects), the signalrecord is reproduced with or without the picture with which it isassociated. During the reproduction of the sound record, the level ofreproduced sound is varied toenhance the dramatic effects thereof inrelation with the associated picture. After one or more rehearsals toobtain the desired series of variations in level and the points ofvariation, a control record of the variations is recorded, which will besubsequently combined with the signal record on the final compositepicture and sound print. Since the control record must be properly timedand thus properly aligned with the signal record, some method and meansfor obtaining synchronization are required.

In the sound recording art, it is well known how synchronization marksmay be applied by the use of clapper-sticks to picture and'soundnegatives during recording. Also, the use of simultaneously energizedfogging lights for the picture and sound negatives is well known.

. However, in the present problem, no picture negative is involved,while one of the films is a sound ently' 'of the recording of thecontrol record. Also, the record being made is unusual sinceit is arecord 01 manual variations which are recorded in the areas intermediatethe sprocket holes.

The principal object of theinvention, therefore, ls to facilitate theproduction or a. control record being reproduced substantiallyindependrecord and the subsequent combining thereof with a signalrecord. a

Another object of the invention is to produce synchronization marks on asignal record and its control record.

A further object of the invention is to improve the marking of a controlrecord for the subsequent combination thereof with a signal record forwhich the control record is madej Although the novel features which arebelieved to be characteristic of this invention are pointed out withparticularity in the appended claims,

the manner of its organization and the mode ofv its operation will bebetter understood by re,-

ferring to the following description read in conjunction with theaccompanying drawing forming a part thereof in which Fig. 1 is adiagrammatic drawing embodying the invention;

for which a. control record is made; and

Fig. 3 is a fragmentary view of a control record made for the signalrecord of Fig. 2.

Referring now to Fig. 1, a film 5 carries a signal record 6 for which acontrol record is to be made. The signal record may be reproduced in anywell known type of manner employing a lamp 8, lenses 9 and I0, and aphotoelectric cell ll. The output of photo-electric cell II is impressedupon an amplifier l2 and then fed to a. variable gain amplifier l4 and arecording amplifier l3, the latter feeding a-loudspeaker 40 and thevariable gain amplifier feeding a loudspeaker l5. For controlling thegain of the variable gain amplifier I4 and consequently the amplitude ofthe signal being reproduced in loudspeaker I 5. an oscillator IB of anysuitable frequency, such as 500 cycles, is connected through apotentiometer 2i and a'rectifier 25 to the variable gain amplifier 14.The output of potentiometer 2| is also impressed upon a rectifier 29 toproduce the control record, as will be explained hereinafter.

The optical portion of the recording system for the control track isshown diagrammatically as including a lamp H, a collecting lens l8, amask IS with an aperture 20 therein, and a. lens 22 for projecting thelight passing the aperture' by a lens 8|: :The form oi the light beampromixer operator.

jected on the mask 26 is shown by the dotted lines 33. v y

The galvanometer 24 has two windings 35 and 36. The winding 35 isconnected to the output of recording amplifier I3 when a switch 38 isclosed, while the winding 36 is permanently connected to the output ofrectifier unit 29. The winding 35 of the alvanometer is adapted to causethe mirror 23 to follow the instantaneous values of the signalmodulations, while the winding 36 causes the mirror to follow therectifier output of the oscillator I6 as varied by the potentiometer 2|.Although the light modulator is shown as a two-winding galvanometer, itis to be understood that noise reduction shutters as disclosed in U. S.Patent No. 2,102,777 of December 21, 1937, may also be used as thecontrol track modulator. Thus, with the switch 38 closed, the light beam33 will be vibrated in accordance with the instantaneous values of thesignal, while with the switch 38 open, the light beam is moved only inaccordance with the variations in the potentiometer 29.

Thus, to produce a control track which is to subsequently control thereproduced level of the signal track independently of the actual levelof the signal track, the film is reproduced through units II, I2, I3,I4, I5 and 40. The variations in light caused by the beam 33 beingvibrated across the slit 21 due to manipulation of the potentiometer 2Iare then impressed upon the sprocket hole area of the film 30. With theswitch 38 closed, any signal being reproduced will be impressed on thewinding 35 and such signal will be recorded, the opening of the switchdiscontinuing such recording. During reproducing of the signal,variations in the normal amplitude level thereof may be varied by thepotentiometer 2| to enhance the dramatic effects of the sound. This isaccomplished by varying the output of the oscillator I5 as impressed onrectifier 25, which controls the gain of variable gain amplifier I4.However, since the output of potentiometer 2I is divided and fed torectifier 29 connected to winding 36, the light beam 33 will be variedin ac-' cordance with the potentiometer or signal variations. film is tobe combined with the signaltrack on film 5, it is necessary thatsynchronizing marks be correspondingly located on the film 5 and film30. This is accomplished as follows:

Referring now to Fig. 2, in which the signal track film 5 is shown, itwill be observed that there is spliced to the upper portion of the film5, a constant frequency modulation tone track 5 of 1000 cycles, afrequency of this approximate value having been found to be particularlydesirable from both the audible and visual standpoints. Its audibilityis desired because the switch 38 is actuated by an operator inaccordance with what he hears in the speaker 40, and it should bereadily visible in order to be detected by the film editors. Thus, sucha section of 1000-cyc1e modulation track is spliced at point 45 to thesignal film.. At the start of recording, the switch 38 is closed and theIOOO-cycle frequency is reproduced in the speaker 40 and simultaneouslyimpressed upon the winding of the galvanometer 24. As soon as thel000-cycle tone disappears, the operator opens the switch 38, and'thecontrol track is then recorded in accordance with the variations ofpotentiometer 2| made by a Although the tone is also reproduced inloudspeaker I5, this speaker is located in. a projection room while therecorder is Since the control track so recorded onat a distant point andthe speaker 40 is required for the recording operator.

The result of this operation produces a control track, the sectionthereof corresponding to Fig. 2 being shown in Fig. 3. It will be notedthat the 1000-cycle tone record is recorded similarly to and in the formof the lOOO-cycle tone record shown in Fig. 2, while the control trackitself is shown during a no-variation period as of constant width. Toillustrate that the signal modulations shown at 44 in Fig. 2 are to bereproduced at a higher than normal level, it will be noted that thecontrol track has gradually narrowed down as shown at 45 in Fig, 3,which, in the final reproduction, will increase the gain of the signalreproducing amplifier in a manner similar to the variations in gain ofthe variable gain amplifier I4 by the varied output of the rectifier 25.

Since the present invention is directed to the production of a controlfilm record for a signal film record and the synchronizing of the twofilm records, it will be noted that these film records are identicallymarked in a manner to facilitate their particularly accurate combinationby the film editors. The two sound films may be first combined into aprint having only the signal and control tracks thereon, or they may besimultaneously printed to the final combination sound and picture print.In either case, the proper relative position of the two tracks may bereadily adjusted.

I claim as my invention:

1. A synchronizing method for marking a control record film beingrecorded with a signal film being reproduced comprising audiblyreproducing a tone and the signal from said signal film in serial order,recording only said tone on said control record during the reproductionthereof, the recording of said tone being discontinued after apredetermined period while continuing the reproduction of said filmbeing reproduced, and recording on said control record the variations inamplitude of said signal record.

2. A system for providing synchronizing marks for a pair of films, onefilm being recorded simul taneously with the reproduction of said otherfilm comprising means for reproducing a tone and a signal from said filmbeing reproduced, said tone being reproduced at a different time fromthat of said signal, means for recording said tone on said film beingrecorded during the time when said tone is being reproduced, and meansfor recording the variations in amplitude of said signal on said filmbeing recorded during the time said signal is being reproduced,

3. A system for providing synchronizing marks on a pair of films, therecords thereon to be combined on a single film comprising means forobtaining a tone record on one of said films, means for reproducing saidtone record, means for recording said tone record on said second film,and

means for discontinuing the recording of said first film to said secondfilm while continuing the reproduction of said first film.

4. A system for producing a control record film for a signal record filmwith synchronizing marks thereon comprising means for obtaining atonerecord on said signal record film, means for reproducing said toneand signal record, means for recording only said tone record on saidfilm; and means for recording the variations made in the normalamplitude of said signal recorg during the reproduction of said signalrecor 5. The method of producing a control record film for a signalrecord film with synchronizing marks thereon comprising attaching a tonerec- 0rd to said signal record film, reproducing said tone and signalrecord in a serial order, recording only said tone record on saidcontrol record film, and recording thereafter on said control recordfilm the variations made in the normal amplitudes of said signal recordduring the reproduction thereof. 1

6. A system for the production of a control record film for, an existingsignal record film comprising means for obtaining a tone record inadvance of said signal record on said signal record film, means fortranslating said tone and signal record into electrical currents, meansfor translating said currents into sound waves, means for recording onlysaid tone currents, means for varying the amplitude of said signalcurrents, and means for recording a record of the variations made in thenormal amplitude of said signal currents during the translation thereofinto sound currents.

7. A system in accordance with claim 6 in which said means for varyingthe amplitude of said signal currents includes an oscillator, arectifierfor said oscillator, a variable gain amplifier for said signal currentsconnected to saidrecti fier, and means for varying the output of saidoscillator as impressed on said' variable gain amplifier to vary theamplification of said signal currents.

8. A system for the production of a control record film for a signalrecord film comprising means for translating said signal record filminto electrical currents, said signalrecord containing therein a tonerecord, means for translating said electrical currents'into sound waves,means for recording only that portion of said signal record filmcontaining said tone record, means for vary,- ing the amplitude of saidsignal current during reproduction, said means including avariable gainamplifier, and means for recording said variations in gainas saidcontrol record.

9. A system in accordance with claim 8 in which said amplifier varyingmeans includes an durlng the reproduction of said signal

